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  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
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<script>
  "use strict";
  // 使用静态方法Object.freeze();来冻结类
  // Object.isFrozen;判断一个对象是否冻结了
  const HOST = {
    url: "https://baidu.com",
    port: 3444
  };
  Object.freeze(HOST);
  HOST.port = 80;
</script>

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